Methods of forming dielectric layers and methods of forming capacitors

ABSTRACT

Methods of forming dielectric layers and methods of forming capacitors are described. In one embodiment, a substrate is placed within a chemical vapor deposition reactor. In the presence of activated fluorine, a dielectric layer is chemical vapor deposited over the substrate and comprises fluorine from the activated fluorine. In another embodiment, a fluorine-comprising material is formed over at least a portion of an internal surface of the reactor. Subsequently, a dielectric layer is chemical vapor deposited over the substrate. During deposition, at least some of the fluorine-comprising material is dislodged from the surface portion and incorporated in the dielectric layer. In another embodiment, the internal surface of the reactor is treated with a gas plasma generated from a source gas comprising fluorine, sufficient to leave some residual fluorine thereover. Subsequently, a substrate is exposed within the reactor to chemical vapor deposition conditions which are effective to form a dielectric layer thereover comprising fluorine from the residual fluorine.

RELATED PATENT DATA

This patent application is a continuation of U.S. patent applicationSer. No. 09/670,984, filed on Sep. 26, 2000, entitled “Methods ofForming Dielectric Layers and Methods of Forming Capacitors”, namingGaro Derderian and Gurtej S. Sandhu as inventors, now U.S. Pat. No.6,319,856, the disclosure of which is incorporated by reference; whichis a continuation of U.S. patent application Ser. No. 09/032,765, filedon Feb. 28, 1998, entitled “Methods of Forming Dielectric Layers andMethods of Forming Capacitors”, naming Garo Derderian and Gurtej S.Sandhu as inventors, now U.S. Pat. No. 6,147,011, the disclosure ofwhich is incorporated by reference.

TECHNICAL FIELD

This invention relates to methods of forming dielectric layers and tomethods of forming capacitors.

BACKGROUND OF THE INVENTION

Dielectric material layers are essential components in integratedcircuitry capacitors, and are typically interposed between two capacitorplates. Capacitors are used in memory circuits, such as dynamic randomaccess memory (DRAM) arrays.

As device dimensions continue to shrink, an important emphasis is placedon maintaining, and in some instances, increasing a capacitor's abilityto store a desirable charge. For example, a capacitor's charge storagecapability can be increased by making the capacitor dielectric thinner,by using an insulator with a larger dielectric constant, or byincreasing the area of the capacitor. Increasing the area of a capacitoris undesirable because the industry emphasis is on reducing overalldevice dimensions. On the other hand, providing a thinner capacitordielectric layer and/or using an insulator with a larger dielectricconstant can present problems associated with current leakage, such asthat which can be caused by Fowler-Nordheim Tunneling. Current leakagecan significantly adversely impact the ability of a capacitor to store acharge.

This invention grew out of needs associated with providing methods offorming dielectric layers having sufficiently high dielectric constants.This invention also grew out of needs associated with providing methodsof forming capacitor constructions which have desirable charge storagecharacteristics, and reduced current leakage.

SUMMARY OF THE INVENTION

Methods of forming dielectric layers and methods of forming capacitorsare described. In one embodiment, a substrate is placed within achemical vapor deposition reactor. In the presence of activatedfluorine, a dielectric layer is chemical vapor deposited over thesubstrate and comprises fluorine from the activated fluorine. In anotherembodiment, a fluorine-comprising material is formed over at least aportion of an internal surface of the reactor. Subsequently, adielectric layer is chemical vapor deposited over the substrate. Duringdeposition, at least some of the fluorine-comprising material isdislodged from the surface portion and incorporated in the dielectriclayer. In another embodiment, the internal surface of the reactor istreated with a gas plasma generated from a source gas comprisingfluorine, sufficient to leave some residual fluorine thereover.Subsequently, a substrate is exposed within the reactor to chemicalvapor deposition conditions which are effective to form a dielectriclayer thereover comprising fluorine from the residual fluorine.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a schematic diagram of a chemical vapor deposition reactor inaccordance with one aspect of the invention.

FIG. 2 is a view of a portion of the reactor.

FIG. 3 is a view of a portion of the reactor.

FIG. 4 is a schematic diagram of another reactor in accordance withanother aspect of the invention.

FIG. 5 is a view of the FIG. 1 reactor at a processing step inaccordance with one aspect of the invention.

FIG. 6 is a diagrammatic side sectional view of a portion of a waferfragment, in process, in accordance with one aspect of the invention.

FIG. 7 is a view of the FIG. 6 wafer fragment at a different processingstep.

FIG. 8 is a graph of capacitance versus leakage current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

Referring to FIG. 1, a chemical vapor deposition reactor is showngenerally at 10. Reactor 10 can comprise any suitable reactor which iscapable of processing substrates as described below. The illustratedreactor includes a pair of electrodes 12, 14 which can be biased by anRF source 16. RF source 16 can be used, in one implementation, togenerate a gas plasma within the reactor. Various other reactor typesand designs, some of which can be used in connection with variousaspects of the invention, are described in a text by Lieberman andLichtenberg, entitled Principles of Plasma Discharges and MaterialsProcessing, the disclosure of which is incorporated by reference.

Reactor 10 is typically used to chemical vapor deposit various layersover a substrate (not shown) and can include a source 18 through whichvarious precursor gases are provided and processed. Such gases can alsobe provided through an electrode, such as electrode 12.

Referring to FIGS. 1-3, reactor 10 includes an internal surface 20 whichdefines a processing chamber in which processing takes place. Theillustrated reactor is depicted at a processing point prior to placementof a substrate therein. A halogen-comprising material, preferably afluorine-comprising material 22 (FIG. 2), 24 (FIG. 3), is formed over atleast a portion of surface 20. In a most preferred aspect,halogen-comprising material comprises activated fluorine. By “activated”is meant that the material can include ions, radicals, electrons, andother excited species having lifetimes which are influenced by variousfactors.

One way of providing the activated fluorine material 22, 24 is togenerate a fluorine-comprising gas plasma having activated fluorinetherein. Such plasma can be generated by introducing afluorine-comprising source gas, such as NF₃, into the reactor, andsubjecting the source gas to processing conditions which are effectiveto form the gas plasma. Such processing conditions can include, in thereactor illustrated in FIG. 1, subjecting the source gas to suitable RFenergy sufficient to form the plasma. Accordingly, internal surface 20is treated with the gas plasma prior to introduction of a substratetherein. Such treatment effectively leaves residual activated fluorineover surface 20 in the absence of a substrate. Accordingly in thisexample, the substrate is not exposed to the gas plasma. Coverage ofsurface 20 by the activated fluorine can be non-uniform, as shown inFIG. 3. Preferably, at least some of the residual activated fluorine ispresent during the chemical vapor depositing of a dielectric layer whichis described just below.

In this example, and because the substrate is not present in the reactorduring formation of the gas plasma, the gas plasma is formed away fromthe substrate. Accordingly, the reactor is preferably substantially, ifnot completely, plasma-free during the depositing of the dielectriclayer. By “substantially” is meant that it can be possible, in somereactor types, for plasma to exist in the reactor substantially remoteof the substrate. Such is more likely to occur with the reactor designillustrated in FIG. 4. There, a reactor 26 includes a remote plasmasource 28 operably coupled therewith. Source 28 is preferably one whichis capable of generating a gas plasma, from the fluorine-comprisingsource gas, which is subsequently flowed into reactor 26. In this way, agas plasma is formed away from any substrate which might be present inFIG. 4. Remote plasma processing and apparatuses for conducting suchprocessing are described in U.S. Pat. No. 5,180,435, entitled “RemotePlasma Enhanced CVD Method and Apparatus for Growing an EpitaxialSemiconductor Layer”, the disclosure of which is incorporated byreference. In the illustrated example, only electrodes 12 a, 14 a areshown. A substrate is not specifically depicted in the FIG. 4 example. Asubstrate could, however, be present in reactor 26 during formation of,and subsequent flowing of the activated fluorine from remote plasmasource 28.

Referring to FIG. 5, a substrate 30 is placed within reactor 10, andpreferably after the internal walls of the reactor have been pre-treatedwith the fluorine-comprising gas plasma. In the presence of activatedfluorine within the reactor, the substrate is exposed to conditionswhich are effective to chemical vapor deposit a dielectric layer overthe substrate which comprises fluorine from the activated fluorine.Processing conditions under which dielectric layers can be depositedinclude using liquid chemical precursors including tantalumpentaethoxide (TAETO) or tantalum tetraethoxide dimethylaminoethoxide(TAT-DMAE), at temperatures from between about 400° C. to 500° C., andpressures from between about 30 mTorr to 30 Torr. Other precursors suchas BST precursors, e.g. M(thd)₂, where M is either Ba or Sr, attemperatures from between about 500° C. to 650° C., and pressures frombetween about 30 mTorr to 30 Torr, can be used.

Preferably, the dielectric layer has a dielectric constant or “k” valuewhich is greater than about 6. Exemplary materials for the dielectriclayer can include silicon nitride (“k” value of around 7), tantalumpentoxide (Ta₂O₅)(“k” values ranging from about 10-25), BST (“k” valuesranging from about 100 to 1000 or greater). The dielectric layerpreferably comprises less than about 10% fluorine, by weight. Morepreferably, the dielectric layer comprises between about 0.001% and 10%fluorine, by weight.

Referring to FIGS. 6 and 7, a capacitor forming method is describedrelative to a substrate 32. Such can comprise any suitable substrateover which a capacitor is to be formed. An exemplary capacitor formed inconnection with dynamic random access memory circuitry includes asubstrate comprising insulative materials, such as borophosphosilicateglass. A first capacitor plate 34 is formed over substrate 32,typically, by chemical vapor deposition of polysilicon. In the presenceof activated fluorine, as described above, a dielectric layer 36 ischemical vapor deposited over first capacitor plate layer 34. A secondcapacitor plate layer 38 is formed over dielectric layer 36 to provide acapacitor construction.

In one reduction-to-practice example, an Applied Materials 5000processing chamber was cleaned, prior to introduction of a substratetherein, with a remote NF₃ plasma under the following processingconditions: 1500 sccm of NF₃, 1800-3200 watts at around 2 Torr for aduration of about 100 seconds. After the plasma clean, a semiconductorwafer was placed in the chamber and a dielectric layer, such as thoselayers described above, was formed over the wafer. The followingconditions were used: temperature of around 475° C. with 300 sccmTAT-DMAE, 250 sccm of O₂, spacing of 350 mils, and a pressure of 1 Torr.

FIG. 8 illustrates, for the reduction-to-practice example, a graph ofcapacitance versus leakage current for two areas over the wafer. Datapoints, collectively grouped at 40, correspond to capacitance andleakage current measurements taken at or near the center of the wafer.Data points, collectively grouped at 42, correspond to capacitance andleakage current measurements taken at or near the edge of the wafer. Asa consequence of the chamber geometry of the Applied Materials 5000chamber, more residual fluorine-comprising material (e.g. activatedfluorine), is prevalent at the edge of the wafer. Hence, the edge of thewafer is more influenced by the above-described treatment than otherwafer portions such as those at or near the center of the wafer.Plotting capacitance versus leakage for the two areas indicates that thecapacitance achieved at or near the edge of the wafer (i.e.,corresponding to data points 42) is generally greater than thecapacitance at or near the center of the wafer (i.e., corresponding todata points 40). In addition, data points 42 constitute wafer areasgenerally having less leakage current for a given capacitance than thosedefined by data points 40. Accordingly, for some of the data points, anoverall increase in capacitance was observed with a lowering of theleakage current. In addition, the deposition rate of the dielectriclayer was observed to increase in the presence of the residual activatedfluorine.

Accordingly, the methods described above permit dielectric layers havingincreased dielectric constants to be formed. Such permits capacitorshaving reduced dimensions to be formed with desirable charge storagecharacteristics.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of forming a dielectric layercomprising: forming a fluorine-comprising material over at least aninterior surface portion of a chemical vapor deposition reactor; andchemical vapor depositing a dielectric layer within the reactor anddislodging at least some of the fluorine-comprising material from theinterior surface portion to incorporate at least some fluorine of thefluorine-comprising material in the dielectric layer.
 2. The method ofclaim 1, wherein forming the fluorine-comprising material comprisesforming activated fluorine over the interior surface portion.
 3. Themethod of claim 1, wherein forming the fluorine-comprising materialcomprises generating a fluorine-comprising gas plasma having activatedfluorine therein which is formed over the interior surface portion. 4.The method of claim 1, wherein forming the fluorine-comprising materialcomprises generating a fluorine-comprising gas plasma remote from thechemical vapor deposition reactor, the gas plasma having activatedfluorine therein, and providing at least some of the activated fluorinefrom the gas plasma over the interior surface portion.
 5. The method ofclaim 1, wherein forming the fluorine-comprising material comprisesgenerating a gas plasma from a source gas comprising NF₃, the plasmahaving activated fluorine therein which is formed over the interiorsurface portion.
 6. The method of claim 1, wherein forming thefluorine-comprising material comprises generating a gas plasma from asource gas consisting of NF₃, the plasma having activated fluorinetherein which is formed over the interior surface portion.
 7. The methodof claim 1, wherein forming the fluorine-comprising material comprisesgenerating a gas plasma from a source gas comprising NF₃, the gas plasmabeing remote from the chemical vapor deposition reactor, the gas plasmahaving activated fluorine therein, and providing at least some of theactivated fluorine from the gas plasma over the interior surfaceportion.
 8. The method of claim 1, wherein chemical vapor depositing adielectric layer comprises depositing a dielectric layer comprisingtantalum pentoxide.
 9. A method of forming a dielectric layercomprising: treating an internal surface of a chemical vapor depositionreactor with a gas plasma generated from a source gas comprising NF₃sufficient to leave some residual fluorine thereover; and exposing aninterior of the reactor to chemical vapor depositing conditionseffective to form a dielectric layer comprising fluorine from theresidual fluorine.
 10. The method of claim 9, wherein at least some ofthe residual fluorine comprises activated fluorine.
 11. The method ofclaim 9, wherein at least some of the residual fluorine comprisesactivated fluorine which is present during the chemical vapor depositingof the dielectric layer.
 12. The method of claim 9, wherein exposing aninterior of the reactor comprises doing so in the absence of the gasplasma.
 13. The method of claim 9, wherein exposing an interior of thereactor comprises exposing a substrate within the reactor to chemicalvapor depositing conditions effective to form the dielectric layerthereover to comprise a material having a dielectric constant greaterthan about six.
 14. The method of claim 9, wherein exposing an interiorof the reactor comprises exposing a substrate within the reactor tochemical vapor depositing conditions effective to form the dielectriclayer thereover to comprise tantalum pentoxide.
 15. The method of claim9, wherein exposing an interior of the reactor comprises exposing asubstrate within the reactor to chemical vapor depositing conditionseffective to form the dielectric layer thereover to comprise less thanabout 10% by weight of fluorine.
 16. The method of claim 9, whereinexposing an interior of the reactor comprises exposing a substratewithin the reactor to chemical vapor depositing conditions effective toform the dielectric layer thereover to comprise between about 0.001% and10% by weight of fluorine.
 17. A method of forming a capacitorcomprising: treating an internal surface of a chemical vapor depositionreactor with a gas plasma generated from a source gas comprisingfluorine sufficient to leave some residual activated fluorine thereover;after said treating, placing a first capacitor plate layer within thechemical vapor deposition reactor; and chemical vapor depositing adielectric layer over the first capacitor plate layer comprising atleast some fluorine from the activated fluorine over the substrate. 18.The method of claim 17, further comprising forming a second capacitorplate layer over the dielectric layer.
 19. The method of claim 17,wherein treating an internal surface comprises forming a gas plasma froma fluorine-comprising source, the gas plasma having at least someactivated fluorine therein which is provided within the reactor.
 20. Themethod of claim 19, wherein the gas plasma is formed away from asubstrate having the first capacitor plate formed thereon.
 21. Themethod of claim 17, wherein treating an internal surface comprises:providing a remote plasma source operably coupled with the reactor; inthe remote plasma source, generating the gas plasma from afluorine-comprising source gas, the plasma including activated fluorine;and flowing activated fluorine from the gas plasma into the reactor. 22.The method of claim 21, wherein a substrate having the first capacitorplate formed thereon is not exposed to the gas plasma.
 23. The method ofclaim 21, wherein the reactor is substantially plasma-free during thedepositing of the dielectric layer.
 24. The method of claim 21, whereindepositing the dielectric layer comprises depositing the dielectriclayer when the reactor is plasma-free.
 25. The method of claim 21,wherein generating a gas plasma comprises generating a gas plasma from agas comprising NF₃.
 26. The method of claim 17, wherein the dielectriclayer comprises material having a dielectric constant greater than aboutsix.
 27. A method of forming a dielectric layer in a chemical vapordeposition reactor comprising: generating a fluorine-comprising gasplasma having activated fluorine therein; disposing some of theactivated fluorine over at least a surface portion of an interior of thereactor; and chemical vapor depositing a dielectric layer within thereactor and dislodging at least some of the activated fluorine from thesurface portion to incorporate at least some fluorine of the activatedfluorine in the dielectric layer.
 28. The method of claim 27, whereingenerating a fluorine-comprising gas plasma comprises generating afluorine-comprising gas plasma remote from the chemical vapor depositionreactor, the gas plasma having activated fluorine therein, and providingat least some of the activated fluorine from the gas plasma over thesurface portion.
 29. The method of claim 27, wherein the dielectriclayer comprises tantalum pentoxide.
 30. A method of forming a dielectriclayer using a chemical vapor deposition reactor comprising: generating afluorine-comprising gas plasma having activated fluorine therein;disposing some of the activated fluorine over at least a surface portionof an interior of the reactor; and chemical vapor depositing adielectric layer comprising tantalum pentoxide within the reactor anddislodging at least some of the activated fluorine from the surfaceportion to incorporate at least some fluorine of the activated fluorinein the dielectric layer.
 31. The method of claim 30, further comprising,after disposing, introducing a substrate into the reactor, whereinchemical vapor depositing comprises chemical vapor depositing thedielectric layer on the substrate.
 32. A method of forming a dielectriclayer comprising: providing a chemical vapor deposition reactor havingan internal surface; treating the internal surface with a gas plasmagenerated from a source gas comprising NF₃ sufficient to leave someresidual activated fluorine thereover; and after said treating, exposingan interior of the reactor to chemical vapor depositing conditions inthe absence of the gas plasma effective to form a dielectric layercomprising fluorine from the residual fluorine, wherein at least some ofthe residual fluorine comprises activated fluorine which is presentduring the chemical vapor depositing of the dielectric layer and whereinthe dielectric layer comprises between about 0.001% and 10% by weight offluorine.
 33. The method of claim 32, wherein the dielectric layercomprises a material having a dielectric constant greater than aboutsix.
 34. The method of claim 32, wherein the dielectric layer comprisestantalum pentoxide.
 35. The method of claim 32, further comprising,prior to exposing, placing a substrate within the reactor, whereinexposing comprises exposing the substrate to chemical vapor depositingconditions in the absence of the gas plasma effective to form adielectric layer on the substrate comprising fluorine from the residualfluorine.